Thanks RJ, I knew I was on the right track. I was able to get the following:
{"rings":[[[38.85976800000159,-77.049912,1.3000000705942512],[38.859774000001586,-77.04989,1.6823160694912076],[38.859762000001595,-77.04989,1.6823160704225302],[38.859762000001595,-77.04989,0.9197780704125762],[38.85977400000157,-77.04989,0.9197780694812536]]],"spatialReference":{"wkid":4326}}
However, ArcGIS Server is telling me that I have too many parts for the shape when I try to construct the geometry. Does the JSON specification support z values for a 3D polygon? I thought it did. I also have a z enabled polygon feature service. Am I missing something here? Does the specification only allow for 4 vertices? or a certain number of significant digits? Thank you.